Our 2000 Outback automatic (new to us in August w/ 150K) had to have the O2 sensor replaced (covered by recall thanks to info found on this site), but only after we paid to have the dealer replace the ignition coil.

 

Two days after ignition coil replacement, the same hesitation and sort of enging sputtering started - read about 02 sensor here, and bingo, problem resolved.

 

It's been two months, we're running the 96? octane Petro Canada winter gas thinking we're doing our part to keep the engine clean.

 

Now we're getting sputtering/hesitation again, and the good old check engine light comes on. Same symptoms that were resolved with 02 sensor replacement last time.

 

Could we be ruining the O2 sensor with the gas we buy? Could we just have very bad luck and had a faulty sensor installed?

 

Any ideas/suggestions?

In the past, Subaru has had problems with faulty O2 sensors. You may very well have a bad sensor. If you can lay your hands on a comprehensive scan tool, you can easily check the O2 sensors.